The present invention relates to the field of papermaking machine felts, and more particularly to methods of forming a seam in a papermakers felt. In papermaking machines, an endless felt structure is supported on and advanced by various machine rolls during the papermaking process. In the papermaking process, such endless felts are employed in a number of capacities such as forming fabrics, as wet press felts and as drying felts. The felts may be woven as endless felts, however, the use of a seam to join the ends of a flat felt into an endless felt is often desirable.
The use of a seam to join the ends of a flat felt is known in the art. Such seams typically include loops or hooks on the end of the felt which are aligned in an alternatingintermeshing relationship and a pintle connector which is inserted through the aligned loops or hooks to close the seam.
The use of metal clips affixed to a seam webbing to form a clipper seam is disclosed in U.S. Pat. No. 4,344,209. The formation of loops, integral with the ends of a flat papermaker's felt through which a pintle can be inserted to join the ends of the felt is disclosed in U.S. Pat. No. 2,883,734.
The use of a pair of shaped pintles freely moveable with respect to one another which each have a convexly curved profile when viewed in cross section, which are inserted through a series of spaced apart loops affixed to the ends of a felt to be joined is disclosed in U.S. Pat. No. 3,668,742. The use of shaped joining elements is shown in the connection of conveyor belt ends by insertion through loops formed by hook members clamped to the belt ends, in U.S. Pat. Nos.: 2,002,897; 2,012,071; and 2,020,542.
As papermaking machines have developed, felts approaching 400 inches in width have come into use. Additionally, over the years, the speed of operation of the felts in such papermaking machines has increased and can often approach the 4 to 5 thousand feet per minute range. Because the felts are threaded around various guides, cylinders, rollers and between presses and further maintained under tension, the strength and durability of a seam becomes a prime consideration. The use of a seam allows for ease of installation of the felt in the papermaking machine. However, the high speed, and conditions of operation, pressure, temperature and moisture, that a seam is exposed to often result in extreme conditions of wear at such seams.
The use of havy pintles which requires increasing the diameter of the loops through which the pintle is inserted can increase seam reliability. However, the resultant increased thickness of the felt at the seam can result in undesirable marking and/or irregularities in the paper product being produced. To control lateral, twisting movement of the felt ends which are joined, a tight fit between the pintle and the seam is desirable.